Metabolic Adaptations of Several Species of Crustaceans and Molluscs to Hypoxia: Tolerance and Microcalorimetric Studies

Abstract

Although some species of fish, crustaceans, and molluscs may behaviorally avoid hypoxic masses of small size and limited duration, others cannot. In a series of crustaceans, tolerance of hypoxia over 28 days at 30°C, decreases as follows: Eurypanopeus depressus (38 Torr = LC50)> Pa!aemonetespugio > Rhithropanopeus harrisii > Penaeus aztecus > Caiinectes sapidus (121 Torr = LC50).Caiinectes sapidus and E. depressus die during 12-hexposure to anoxia and their heat dissipation rates (quantified by microcalorimetry) are depressed in seawater at 25%air saturation (normoxia) to only 32 and 47% of their metabolic rate at normoxia. In contrast, starved Crassostrea virginica and Thais haemastoma are anoxia tolerant; their metabolic rates are depressed un der anoxia to 75%and 9%ofthe normoxic rate. Hypoxia tolerance is greater at 20°C than at 30°C for Penaeus az tecus and Crassostrea virginica, but no temperature effect on tolerance exists for Caiinectes sapidus. Hyp oxia tolerance varies inversely with salinity for Penaeus aztecus at 20° and 30°C and for Caiinectes sapidus at 30°C, but it varies directly with salinity at 20°C in Caii nectes sapidus. Greater depression of metabolic rate oc curs in molluscs during anoxia exposure (and is corre batedwith greater hypoxia tolerance) than occurs in Cal !inectes sapidus and Penaeus aztecus, which are not anoxia tolerant. Heavy mortality probably occurs in young Caiinectes sapidus and Penaeus aztecus and in